A species dossier for this lichen was produced by A.M. Fryday and B.J. Coppins in 1999 for Scottish Natural Heritage and the Royal Botanic Garden Edinburgh. This dossier reports in detail the world distribution and status, identification and ecology of the Tarn Lecanora and should be consulted. In summary they report this lichen to be confined to Europe with a concentration of sites in Scandinavia and a very local distribution elsewhere.
It produces loosely attached yellow to pale yellow-green, rosette-like lobed thalli on rocks in the splash zone of upland lakes and rarely in the flood zone of upland rivers. Apothecia are usually abundant in the thallus centre. They are dish like with a yellow crenate and wavy margin around a rose-brown to brown, non-pruinose disc.
It somewhat resembles Lecanora muralis which can occur in the same habitat. L. achariana is less appressed to the rock with lobes that tend to overlap towards the centre of the thallus giving it a chunkier appearance and the thallus is more yellow-green. Vince Giavarina says it appears in looks to be intermediate between L. muralis and Squamarina cartilaginea. The apothecia are also paler in colour than in L. muralis. RGW
|Photos: Alan Orange|